Elucidation of the basic immune mechanisms involved in induced protection against tuberculosis is the primary objective of this project. The roles of various fractions (PPD and trehalose mycolates) of mycobacteria in stimulation immunity are investigated to establish interrelationships between pulmonary granuloma, delayed-type hypersensitivity, cell-mediated immunity and protection in the mouse model system. The further role of P3 in properly presenting for the selective induction of cell-mediated immunity is being investigated. The role of soluble antigen in abrogating protection and delayed-type hypersensitivity is also studied.